Wilms' Tumor Overview & Types - OmniMedicalSearch.com

Conditions & Diseases: Cancers

Kidney Cancer - Wilms' Tumor

Wilms’ Tumor Overview

Wilms’ tumor, also called nephroblastoma, is the most common type of kidney cancer that affects children. It is listed as a rare diseased by the Office of Rare Diseases of the National Institute of Health because it affects less than 200,000 people in the US population. Approximately 5.6 percent of the "children cancers" are Wilms’ tumors.

It predominantly occurs in the first five years of the child's life, especially around age three or four (which is the peak age for this type of cancer), and rarely occurs in children older than 8 years. It usually affects only one kidney, but in few cases (5 percent) tumors occur in both kidneys.

Unfortunately, Wilm’s tumor is diagnosed only when the tumor(s) is/are already big, but before the cancer metastasize (spread throughout the body). The average weight of a Wilms’ tumor when discovered is around one pound, but in some cases can be larger than the kidney where it developed.

Kidneys start to develop before the baby is born, when the kidney’s cells are not yet differentiated into various mature kidney cells. These undifferentiated cells mature in time, some before the moment of birth, some after the baby was born. The maturation process of the kidney cells ends around the age of three or four. However, this maturation process can be impaired, and some of these undifferentiated cells grow and divide uncontrollably and exaggerated causing tumors to form.

Wilms’ Tumor Types

The Wilm’s tumors are classified in two major types, according to the cancerous cells' appearance when examined under a microscope (histology).

1. Wilms’ tumor with a favorable appearance.

This is a common type of Wilms' tumor. Around 95 percent of the children that suffer from kidney cancer have a favorable histology. When examined under microscope, the cells of a favorable appearance Wilms’ tumor are uniform and do not vary inappearance. This type of cancer responds well to treatment.

2. Wilms’ tumor with an unfavorable appearance.

When examined under microscope, the cells of an unfavorable appearance Wilms’ tumor have two distinctive features: (1) the cancerous cell nuclei (the central part of a cell that contains the DNA) are large and distorted, and (2) the cancerous cells are not uniform and their appearance varies (anaplasia). When the anaplasia is significant, the treatment outcome is poor.

In addition to Wilms' tumor, there are two other types of children kidney cancers, which initially were classified as Wilms' tumors with unfavorable histology (appearance), but now they are classified separately.

Clear cell sarcoma of kidney (CCSK) is a malignant renal tumor that affects children with a tendency to metastasize to bones and othre organs. The avarage age of diagnosis is between 2 and 4 years old.
Rhabdoid tumor is a rare and highly malignant tumor that affects children. The avarage age of diagnosis is around the age 3, but the risk age for this type of cancer range between 2 and 13 years old. This type of tumor equally affects males and females.

These two children kidney cancers have a poor prognosis when the cancer has spread beyond the kidney. The treatment approach for clear cell sarcoma of the kidney and rhabdoid tumor is similar with Wilms’ tumors only more intensively.

Article by Alina Morrow, MS
Medical Writer
OmniMedicalSearch.com